Differential signaling is a method of transmitting information electrically by means of two complementary signals sent on two separate traces in which a receiving device reads the difference between the two signals. Since the receiver ignores the traces' voltages with respect to ground, small changes in ground potential between transmitter and receiver do not affect the receiver's ability to detect the signal.
A driver is generally used to provide a differential signal for transmission to a receiver. A large number of factors may affect the quality and characteristics of the signal produced, such as skew, reflections, pattern-dependent interference, propagation delays, and coupled noise, among others. Noise may be coupled onto a signal from a number of sources and may vary as the frequency of the signal varies. Reflections may radiate back and forth on a transmission line due to termination impedance mismatches and may also be dependent on the frequency of the signal. Crosstalk is induced by the electromagnetic fields generated by nearby signals, producing impedance changes in components and transmission lines. A pre-driver may modify the input signal used by the driver in order to improve the characteristics and/or quality of the communication signal.